Enter your Room Length, Width, Ceiling Height, Room Type, Occupants, Insulation Quality, Sun Exposure, and Local Climate into the AC BTU Calculator to find your Required BTU/hr, Room Area, BTU per Sq Ft, and Recommended AC Capacity in tons.
Required BTU/hr
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Room Area
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BTU per Square Foot
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Recommended AC Capacity
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A BTU (British Thermal Unit) is a measurement of energy. In air conditioning, it represents the amount of heat an AC unit can remove from a room per hour. Higher BTU ratings mean more cooling power.
An undersized AC will struggle to cool your room effectively, run continuously, consume more energy, and may overheat or break down prematurely due to overwork.
An oversized AC will cool the room too quickly without removing enough moisture, making it feel clammy and uncomfortable. It will also cycle on and off frequently, wasting energy and reducing the unit's lifespan.
Multiply the room's length by its width in feet. For example, a 12ft x 10ft room has 120 square feet. For irregularly shaped rooms, break them into rectangles and add the areas together.
Portable AC units are typically less efficient than window units, so you may need 10-15% higher BTU capacity. Also consider that portable units generate some heat indoors and require proper exhaust ventilation.
Key factors include ceiling height, insulation quality, sun exposure, number of occupants, appliances that generate heat, and your local climate. Kitchens and top floors typically need more cooling capacity.
The general rule is 20 BTU per square foot, but this varies based on ceiling height, insulation, sun exposure, and climate. Well-insulated rooms may need only 15 BTU/sq ft, while poorly insulated sunny rooms may need 25+ BTU/sq ft.
An 8000 BTU air conditioner can typically cool a room of 300-400 square feet with average conditions. This works well for most bedrooms, small living rooms, or offices with standard 8-9 foot ceilings.